The present invention relates to processes for the oxidation of a compound having a terminal carbon-carbon double bond, for example, an alpha olefin, to produce the corresponding aldehyde. In particular, the invention relates to such processes in which the compound is contacted with molecular oxygen in the presence of a Group VIII metal component.
Palladium chloride has been known since 1894 to stoichiometrically oxidize ethylene to acetaldehyde in the presence of water. Co-catalysts, such as CuCl.sub.2, could reoxidize the elemental palladium, Pd(O), that was formed back to the active palladium, Pd(II), have been added to provide enhanced results.
Palladium-based oxidation reactions have been extended to higher olefins. Under most conditions, only methyl ketones are formed from alpha olefins. However, aldehydes have been observed in the stoichiometric reactions with palladium salts.
Aldehydes produced from compounds having terminal carbon-carbon double bonds are useful for many purposes, for example, in pharmaceuticals, flavors and fragrances. In addition, such aldehydes can be employed as precursors or intermediates for other valuable products. For example, 3-acetoxypropionaldehyde may be used as a precursor for 1,3-propanediol.
It would be advantageous to provide effective and efficient processes for the production of aldehydes from compounds having a terminal carbon-carbon double bond, such as alpha olefins.
Feringa U.S. Pat. No. 4,661,642 discloses a process for the oxidation of alpha olefins to the corresponding aldehyde and ketone. The process involves contacting the alpha olefin and molecular oxygen in the presence of a solution of a Group VIII metal complex containing at least one NO.sub.2 or NO ligand, a divalent copper salt and a tertiary alcohol as solvent. The results presented in this patent indicate that 1-decene can be oxygenated to a 60:40 (molar) mixture of aldehyde to ketone after 1.1 hours, although the ratio dropped to 18:82 after 2.1 hours. The NO.sub.2 or NO ligand-containing complex is made using stoichiometric silver, thus increasing the cost of the catalyst. In addition, only about 7 turnovers, that is, mols of aldehyde plus ketone per mol of palladium, were achieved before the catalysts described in this patent became ineffective. Processes which provide increased selectivities to and yields of aldehydes and/or increased numbers of turnovers are desirable from effectiveness and efficiency standpoints.